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inviting rodents to live in them as formerly. Scarcely less important, 

 access should be stopped. Catch-basin feeding sewers should be 

 constructed so that rats can not slip through into the mains, or haviiig 

 once gotten in, they can not escape, and hence must drown. Farms 

 are frequently protected against rodent migrations by tin or zinc 

 sheeting sunk into the ground about a- foot and a half and standing 

 about the same height above the surface along the fence line. 



Finally, as the progress of rodents from place to place within com- 

 munities must be hindered, so must they be stopped from entering 

 new communities. Railroads and seagoing vessels carry great 

 numbers of rats in freight. The rat-proof compounds above described 

 serve well enough so far as railroads are concerned. With vessels 

 it is a different matter, and one demanding special attention, since 

 the rodent is only too likely to import infection from foreign harbors. 

 All hawsers thrown out to make boats fast should be provided with 

 traps to catch any rat seeking to land along the hawser. San 

 Francisco, about to possess a rat-proof water front, is now building 

 concrete wharves to prevent the landing of rodents. Every port 

 should be safeguarded by stone, concrete, or iron wharves and piers. 

 As a further protection, all ships should have permanent devices, as is 

 now proposed for naval construction. Levy's system of metal 

 conduits built into vessels promises much in the present world-wide 

 war upon rodents. Rodents must be "built out of existence," 

 and to eradicate rats for all time we must erect wide systems of 

 municipal fortifications. 



